A microfluidic chip and its use in characterising the particle-scale behaviour of microbial-induced calcium carbonate precipitation (MICP)

Microbial-Induced Carbonate Precipitation (MICP) is an innovative ground improvement technique which can enhance the strength and stiffness of soils, and can also control their hydraulic conductivity. These engineering properties of MICP-treated soils are affected by particle-scale behaviour of the precipitated carbonate, i.e. composition, amount and distribution, which are controlled by the MICP process occurring at the particle-scale. In this study, we designed and fabricated a microfluidic chip to improve our understanding of MICP at particle-scale by observing the behaviour of bacteria and CaCO3 crystals during this process. We found that bacteria became evenly distributed throughout the microfluidic chip after the injection of bacterial suspension, grew during bacterial settling, and detached during the injection of cementation solution. Bacteria aggregated during the cementation solution injection, and CaCO3 crystals formed at narrow pore throats or open pore bodies either during or after cementation solution injections.